1. Technological Field Of The Invention
The present invention relates to the field of manufacturing products, such as semiconductor chips, and more particularly, to a method and apparatus for controlling a manufacturing process and sensing parameters related to that process.
2. Description Of Related Art
The manufacture of most products, such as wafers containing semiconductor devices, requires a number of discrete processing steps to create the product. For the example of wafers, a number of discrete steps are needed to produce a packaged semiconductor circuit device from raw semiconductor material. The starting substrate is usually a slice of single crystal silicon referred to as a wafer. Circuits of a particular type are fabricated together in batches of wafers called "lots" or "runs". The fabrication process creates regular arrays of a circuit on the wafers of a lot. During processing, the individual wafers in a lot may go through individual processing steps one at a time or as a batch. At the completion of wafer processing the wafers are tested to determine circuit functionality. Later the wafers are sliced, the functioning products are packaged, and further testing occurs prior to use by the customer.
Data gathered during the course of wafer processing is used to diagnose yield problems and forms the basis of yield improvement efforts. For example, during semiconductor processing, particle contamination in the processing tool will normally have a deleterious effect on product yield. In order to collect data on particle contamination, a sensor may be used that senses the level of particle contamination in the processing tool chamber, in the outflow gas, or other area.
In known arrangements, the in situ sensor for measuring a parameter or operating condition, such as particle contamination, is controlled independently of the processing tool. This sensor also has its own separate database for storing the sensor data that is collected during the manufacturing processing step performed by the processing tool. The processing tool is controlled by a computer, separate from the sensor controller, and has its own database which stores information that identifies the lot that is being processed and the processing tool. This information, known as the lot and entity record, may also contain certain data such as when the processing began, ended, etc.
One of the problems with this known arrangement is the extreme difficulty in correlating the specific lot with the particle measuring data that has been sensed and stored by the sensor. This may occur, for example, since the time stamp of the computer controlling the processing tool is often not synchronized with the time stamp for the database associated with the sensor. It then becomes a painstaking process for a person to manually correlate the sensor data with the lot data. The expense involved in correlating the sensor data with the lot data may be greater than the value of the information that can be gleaned from the correlated data.
Another disadvantage of the known system is the independence of the sensor control and sensor data from the computer that operates the processing tool. Since the computer receives no information regarding, for example, particle contamination during the manufacturing processing step, changing the operation of the processing tool or halting the operation altogether if the particle contamination is too high may not be performed until only after a number of lots have been processed and the defects determined.